Metal trace fabrication for optical element

ABSTRACT

A system may include an optical element including a surface defining a recess, conductive material disposed within the recess, and a solder mask disposed over a portion of the conductive material. The solder mask may define an aperture through which light from the optical element may pass. Some aspects provide creation of an optical element including a surface defining a recess, deposition of conductive material on the surface such that a portion of the deposited conductive material is disposed within the recess, and substantial planarization of the surface to expose the portion of the conductive material disposed within the recess.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 12/909,488, filed on Oct. 21, 2010 and entitled “Metal TraceFabrication For Optical Element” which is a divisional of U.S. patentapplication Ser. No. 11/782,609, filed on Jul. 24, 2007 and entitled“Metal Trace Fabrication For Optical Element” which claims priority toU.S. Provisional Patent Application Ser. No. 60/899,150, filed on Feb.2, 2007 and entitled “Concentrated Photovoltaic Energy Designs”, thecontents of which are incorporated herein by reference for all purposes.

BACKGROUND

1. Field

Some embodiments generally relate to electrical systems incorporatingone or more optical elements. More specifically, embodiments may relateto an optical element efficiently adapted for interconnection toelectrical devices.

2. Brief Description

In some conventional devices, an optical element (e.g., a lens) mayinclude metal traces for interconnection to an electrical circuit. Themetal traces may be fabricated on and/or within the optical elementusing any of several known techniques. For example, the metal traces maybe deposited using thin or thick film lithography. Lithography, however,requires expensive equipment and time-consuming processes.

Since a typical optical element does not include distinguishing surfacefeatures, lithographic techniques also require fiducial marks for properalignment of the metal traces on the optical element. However, theplacement of the fiducial marks on the optical element is also difficultdue to the lack of surface features and the material of which theoptical element is composed (e.g., glass).

What is needed is a system to efficiently incorporate metal traces intoan optical element.

SUMMARY

To address at least the foregoing, some aspects provide a method, meansand/or process steps to create an optical element including a surfacedefining a recess, deposit conductive material on the surface such thata portion of the deposited conductive material is disposed within therecess, and substantially planarize the surface to expose the portion ofthe conductive material disposed within the recess.

Creation of the optical element may include molding the optical elementwith a mold defining the optical element and the recess. Also oralternatively, deposition of the conductive material may include placinga stencil on the optical element prior to metal spraying the conductivematerial onto the optical element.

In some aspects, a reflective material is deposited on the opticalelement and not on the surface, an electrical isolator is deposited onthe reflective material but not on the surface, and the conductivematerial is deposited on the electrical isolator. Aspects may includedeposition of a solder mask over the exposed portion of the conductivematerial, wherein the solder mask defines an aperture through whichlight from the optical element may pass. Further to the foregoingaspects, a terminal of a solar cell may be coupled to the exposedportion of the conductive material such that a portion of the solar cellis disposed over the aperture.

In other aspects, provided are an optical element including a surfacedefining a recess, conductive material disposed within the recess, and asolder mask disposed over a portion of the conductive material. Thesolder mask may define an aperture through which light from the opticalelement may pass. The optical element may comprise a transparent portionincluding the surface, and light may pass from the transparent portionthrough the aperture.

According to further aspects, a reflective material may be disposed onthe optical element and not on the surface, an electrical isolator maybe disposed on the reflective material and not on the surface, andsecond conductive material may be disposed on the electrical isolator.Some aspects include a solar cell having a terminal coupled to a portionof the conductive material exposed by the aperture, wherein a portion ofthe solar cell is disposed to receive the light from the aperture.

The claims are not limited to the disclosed embodiments, however, asthose in the art can readily adapt the description herein to createother embodiments and applications.

BRIEF DESCRIPTION OF THE DRAWINGS

The construction and usage of embodiments will become readily apparentfrom consideration of the following specification as illustrated in theaccompanying drawings, in which like reference numerals designate likeparts.

FIG. 1 is a flow diagram of a method according to some embodiments.

FIG. 2 is a perspective view of a portion of an optical elementaccording to some embodiments.

FIG. 3 is a cross-sectional view of a portion of an optical elementaccording to some embodiments.

FIG. 4 is a perspective view of a portion of an optical element withconductive material disposed thereon according to some embodiments.

FIG. 5 is a cross-sectional view of a portion of an optical element withconductive material disposed thereon according to some embodiments.

FIG. 6 is a perspective view of a substantially planarized portion of anoptical element according to some embodiments.

FIG. 7 is a cross-sectional view of a substantially planarized portionof an optical element according to some embodiments.

FIG. 8 is a flow diagram of a method according to some embodiments.

FIG. 9A is a perspective view of a transparent optical element accordingto some embodiments.

FIG. 9B is a cross-sectional view of a transparent optical elementaccording to some embodiments.

FIG. 10A is a perspective view of a transparent optical element withreflective material disposed thereon according to some embodiments.

FIG. 10B is a cross-sectional view of a transparent optical element withreflective material disposed thereon according to some embodiments.

FIG. 11A is a perspective view of an optical element with an electricalisolator disposed thereon according to some embodiments.

FIG. 11B is a cross-sectional view of an optical element with anelectrical isolator disposed thereon according to some embodiments.

FIG. 12A is a perspective view of an optical element with conductivematerial disposed thereon according to some embodiments.

FIG. 12B is a cross-sectional view of an optical element with conductivematerial disposed thereon according to some embodiments.

FIG. 13A is a perspective view of an optical element after planarizationof a portion thereof according to some embodiments.

FIG. 13B is a cross-sectional view of an optical element afterplanarization of a portion thereof according to some embodiments.

FIG. 14A is a perspective view of a solder mask deposited on an opticalelement according to some embodiments.

FIG. 14B is a cross-sectional view of a solder mask deposited on anoptical element according to some embodiments.

FIG. 15 is a close-up cross-sectional view of an optical elementincluding a solar cell according to some embodiments.

DETAILED DESCRIPTION

The following description is provided to enable any person in the art tomake and use the described embodiments and sets forth the best modecontemplated for carrying out some embodiments. Various modifications,however, will remain readily apparent to those in the art.

FIG. 1 is a flow diagram of process 10 according to some embodiments.Process 10 may be performed by any combination of machine, hardware,software and manual means.

Initially, an optical element is created at S12. The optical elementincludes a surface defining a recess, and may be composed of anysuitable material or combination of materials. According to someembodiments, the optical element may be configured to manipulate and/orpass desired wavelengths of light. The optical element may comprise anynumber of disparate materials and/or elements (e.g., lenses, mirrors,etc.) according to some embodiments.

The optical element may be created using any combination of devices andsystems that is or becomes known. Some embodiments of S12 includedepositing a liquid or powder into a mold and cooling, heating and/orpressuring the mold. The mold may define the optical element as well asthe aforementioned recesses. Alternatively, the recesses may be formed(e.g., by etching, milling, etc.) after the optical element is molded.

FIG. 2 is a perspective view of a portion of optical element 100according to some embodiments, and FIG. 3 is a cross-sectional view ofoptical element 100. FIGS. 2 and 3 show only a portion of opticalelement 100 in order to illustrate that optical element 100 may exhibitany suitable shape or size. Element 100 may be fabricated according toS12 of FIG. 1, but S12 is not limited thereto.

The illustrated portion of optical element 100 comprises surface 110,recess 120 and recess 130. In the present description, surface 110includes portions of element 100 which define recess 120 and recess 130.As mentioned above, recess 120 and recess 130 may have been defined by amold used to create optical element 100 or formed after creation ofoptical element 100.

Returning to process 10, conductive material is deposited on the surfaceof the optical element at S14. The material is deposited such that aportion of the deposited material is disposed within the defined recess.The conductive material may be composed of any combination of one ormore materials. In some embodiments, the conductive material comprisesnickel. Moreover, the conductive material may be deposited using anysuitable process that is or becomes known, including but not limited tosputtering, chemical vapor deposition, sol gel techniques and thermalspraying (e.g., twin wire arcing, plasma spraying).

FIG. 4 is a perspective view of optical element 100 after S14 accordingto some embodiments. FIG. 5 is a cross-sectional view of optical element100 as shown in FIG. 4. Conductive material 140 is depicted coveringsurface 110 of element 100.

Conductive material 140 is disposed within the recesses defined bysurface 110. A thickness of material 140 within recesses 120 and 130 isgreater than a thickness of material 140 on other portions of surface110, but embodiments are not limited thereto. Moreover, a thickness ofmaterial 140 on the other portions of surface 110 need not be as uniformas shown in FIG. 5. Generally, a height of conductive material 140 onvarious portions of surface 110 may depend on the technique used todeposit material 140 at S14.

The surface of the optical element is substantially planarized at S16.The planarization exposes the portion of the conductive materialdisposed within the recess. Chemical-mechanical polishing may beemployed at S16 to substantially planarize the surface, but embodimentsare not limited thereto. Planarization may comprise removing anuppermost portion of the surface of the optical element as well as anupper layer of the conductive material.

FIGS. 6 and 7 depict element 100 after some embodiments of S16. Asshown, conductive material 140 is disposed within recess 120 and recess130 and is substantially flush with adjacent portions of surface 110.According to some embodiments, conductive material 140 may beelectrically coupled to an electrical device and/or to other conductivetraces.

FIG. 8 is a flow diagram of process 200 according to some embodiments.Process 200 may be performed by any combination of machine, hardware,software and manual means.

Process 200 begins at S210, at which an optical element is created. Asdescribed with respect to S12, the optical element includes a surfacedefining a recess, and may be composed of any suitable material orcombination of materials. The optical element may be created using anycombination of devices and systems that is or becomes known.

FIG. 9A is a perspective view of optical element 300 created at S210according to some embodiments, and FIG. 9B is a cross-sectional view ofelement 300. Optical element 300 may be molded from low-iron glass atS210 using known methods. Alternatively, separate pieces may be glued orotherwise coupled together to form element 300. Optical element 300 maycomprise an element of a solar concentrator according to someembodiments.

Element 300 includes convex surface 310, pedestal 320 defining recesses322, 324, 326 and 328, and concave surface 330. Recesses 322, 324, 326and 328 may have been defined by a mold used to create optical element300 or formed after creation of optical element 300. The purposes ofeach portion of element 300 during operation according to someembodiments will become evident from the description below.

A reflective material is deposited on the optical element at S220. Thereflective material may be intended to create one or more mirroredsurfaces. Any suitable reflective material may be used, taking intoaccount factors such as but not limited to the wavelengths of light tobe reflected, bonding of the reflective material to the optical element,and cost. The reflective material may be deposited by sputtering orliquid deposition.

FIGS. 10A and 10B show perspective and cross-sectional views,respectively, of optical element 300 after some embodiments of S220.Reflective material 340 is deposited on convex surface 310 and concavesurface 330. Reflective material 340 may comprise sputtered silver oraluminum. The vertical and horizontal surfaces of pedestal 320 may bemasked at S220 such that reflective material 340 is not depositedthereon, or otherwise treated to remove any reflective material 340 thatis deposited thereon.

Next, at S230, an electrical insulator is deposited on the opticalelement. The insulator may comprise any suitable insulator orinsulators. Non-exhaustive examples include polymers, dielectrics,polyester, epoxy and polyurethane. The insulator may be deposited usingany process that is or becomes known. In some embodiments, the insulatoris powder-coated onto the optical element.

Some embodiments of S230 are depicted in FIGS. 11A and 11B. Insulator350 is deposited on convex surface 310 or, more particularly, onreflective material 340. Again, S230 is executed such that insulator 350is not deposited on the vertical and horizontal surfaces of pedestal320. According to the illustrated embodiment, insulator 340 is notdeposited on concave surface 330 (i.e., on reflective material 340deposited on concave surface 330).

Returning to process 200, a pattern of conductive material is depositedon the surface and the electrical isolator at S240 such that a portionof the deposited conductive material is disposed within the definedrecess. The conductive material may be composed of any combination ofone or more materials (e.g., nickel, copper). Sputtering, chemical vapordeposition, thermal spraying, lithography, and or other techniques maybe used at S240 to deposit the conductive material on the surface and onthe electrical isolator.

FIG. 12A is a perspective view and FIG. 12B is a cross-sectional view ofoptical element 300 after S240 according to some embodiments. Conductivematerial 360 covers pedestal 320 and portions of insulator 350. FIG. 12Bshows conductive material 360 disposed within recesses 322 and 326.Conductive material 360 disposed in recesses 322 and 326 is contiguouswith, and therefore electrically connected to, conductive material 360disposed on insulator 350. Although conductive material 360 appears toextend to a uniform height above element 300, this height need not beuniform.

Conductive material 370, which may be different from or identical tomaterial 360, also covers portions of insulator 350. Conductive material360 and conductive material 370 define a gap to facilitate electricalisolation from one another. Embodiments such as that depicted in FIGS.12A and 12B may include placing a stencil in the shape of theillustrated gap on electrical isolator 350 and depositing conductivematerial 360 and 370 where shown and on the stencil. Removal of thestencil may then result in the apparatus of FIGS. 12A and 12B.

Conductive materials 360 and 370 may create a conductive path forelectrical current generated by a photovoltaic (solar) cell coupled toelement 300. Conductive material 360 and conductive material 370 mayalso, as described in U.S. Patent Application Publication No.2006/0231133, electrically link solar cells of adjacent solarconcentrators in a solar concentrator array.

At S250, the surface of the optical element is substantially planarizedto expose the portion of the conductive material disposed within therecess. Planarization may comprise chemical-mechanical polishing or anyother suitable system. As described above, planarization may alsocomprise removing an uppermost portion of the surface of the opticalelement as well as an upper layer of the conductive material.

FIGS. 13A and 13B show optical element 300 after some embodiments ofS250. Conductive material 360 remains disposed within recesses 322through 328 and electrically coupled to conductive material 360deposited on electrical isolator 350. Conductive material 360 disposedwithin recesses 322 through 328 is also substantially flush withadjacent portions of pedestal 320.

According to some embodiments, S240 and S250 may comprise placing amaterial (e.g., wax, polymer) on areas of surface 320 other thanrecesses 322, 324, 326 and 328. The material may comprise a materialwhich resists adhesion to the conductive material. The material may bedip-coated, contact-printed, stamped, rolled, painted, etc. onto surface320.

Conductive material 360 may be thereafter deposited onto the materialand recesses 322, 324, 326 and 328. The material is then removed using achemical stripping method, for example, thereby removing any conductivematerial that has adhered to the material.

After formation of apparatus 300 of FIGS. 13A and 13B, a solder maskdefining an aperture is deposited over the exposed portion of theconductive material at S260. The solder mask may protect the surfacesurrounding the conductive material during subsequent soldering ofelectrical contacts to the exposed conductive portions. The solder maskmay be deposited using a stencil and a ceramic spray and/or may bedeposited using photolithographic techniques.

FIGS. 14A and 14B show a perspective view and a cross-sectional view,respectively, of optical element 300 including solder mask 380. Soldermask 380 defines aperture 385 through which portions of conductivematerial 360 are visible. Solder mask 380 may therefore allow solderingof electrical elements to the visible portions while protecting otherportions of conductive material 360.

In this regard, a terminal of a solar cell is coupled to the exposedportion of the conductive material at S270. The terminal may be coupledsuch that a portion of the solar cell is disposed over the aperture. Theportion of the solar cell may comprise an area for receiving photonsfrom which the solar cell generates electrical current.

FIG. 15 is a close-up cross-sectional view of element 300 after S270according to some embodiments. Solar cell 390 may comprise a solar cell(e.g., a III-V cell, II-VI cell, etc.) for receiving photons fromoptical element 300 and generating electrical charge carriers inresponse thereto. Solar cell 390 may comprise any number of active,dielectric and metallization layers, and may be fabricated using anysuitable methods that are or become known.

Solder bumps 392 and 394 are coupled to conductive material 360 disposedin recesses 322 and 326, respectively. Solder bumps 392 and 394 are alsorespectively coupled to terminals 393 and 395 of solar cell 390. Variousflip-chip bonding techniques may be employed in some embodiments toelectrically and physically couple terminals 393 and 395 to theconductive material disposed in recesses 322 and 326. In someembodiments, unshown terminals of solar cell 390 are coupled toconductive material 360 disposed in recesses 324 and 328 of element 300.

According to some embodiments, a protection layer is applied to theexposed portions of conductive material 360 disposed in recesses 322through 328 prior to S270. The protection layer may comprise a lowerlayer of nickel and an upper layer of gold. A portion of the gold layermay dissipate during coupling of the terminal at S270.

Some embodiments may avoid deposition of solder mask 380 at S260 byreplacing solder bumps 392 and 394 by other interconnects that do notrequire melting to couple terminals 393 and 395 to conductive material360 disposed in recesses 322 and 326. Examples of such materials includegold stud bumps and conductive die attaches including silver-filledepoxy. In these embodiments, the coupling may be established by knownmethods such as ultrasonic welding and other direct chip attachmentmethods.

According to some embodiments, a thin layer of conductive material isdeposited on entire surfaces 310 and 320 of optical element 300.Photoresist is then applied to entire surfaces 310 and 320. Thephotoresist is patterned and developed such that the photoresist coversall portions of the conductive material except for exposed portionswhere metal traces are desired. Metal plating is applied which adheresto the exposed portions but not to the photoresist. The photoresist isthen removed, and the thin layer of conductive material is removed. Thethin layer may be removed by selectively etching in a case that the thinmaterial differs from the metal plating material. In some embodiments,etch time may be controlled to remove the thin layer while leaving asuitable thickness of the metal traces.

Apparatus 300 may generally operate in accordance with the descriptionof aforementioned U.S. Patent Application Publication No. 2006/0231133.With reference to FIG. 15, solar rays enter surface 398 and arereflected by reflective material 340 disposed on convex surface 310. Therays are reflected toward reflective material 340 on concave surface330, and are thereafter reflected toward aperture 385. The reflectedrays pass through aperture 385 and are received by window 396 of solarcell 390. Those skilled in the art of optics will recognize thatcombinations of one or more other surface shapes may be utilized toconcentrate solar rays onto a solar cell.

Solar cell 390 receives a substantial portion of the photon energyreceived at surface 398 and generates electrical current in response tothe received photon energy. The electrical current may be passed toexternal circuitry (and/or to similar serially-connected apparatuses)through conductive material 360 and conductive material 370. In thisregard, solar cell 390 may also comprise a terminal electrically coupledto conductive material 370. Such a terminal would exhibit a polarityopposite to the polarity of terminals 393 and 395.

The several embodiments described herein are solely for the purpose ofillustration. Embodiments may include any currently or hereafter-knownversions of the elements described herein. Therefore, persons in the artwill recognize from this description that other embodiments may bepracticed with various modifications and alterations.

The invention claimed is:
 1. A method comprising: depositing a firstconductive material on a solid optical element consisting essentially ofglass having a flat first surface including a concave surface portion, aconvex second surface disposed opposite to the flat first surface, and acylindrical pedestal structure disposed on the concave surface portion,the cylindrical pedestal structure including a flat second surface thatfaces away from the flat first surface and defines at least oneelongated radial recess, wherein depositing the first conductivematerial comprises depositing the first conductive material on the flatsecond surface of the cylindrical pedestal structure such that at leasta portion of the first conductive material is disposed in the at leastone elongated radial recess; depositing photoresist on the firstconductive material; removing a portion of the photoresist to expose theportion of the first conductive material disposed in the at least oneelongated radial recess; plating the exposed portion of the firstconductive material with a second conductive material; removing aremaining portion of the photoresist; and removing unplated portions ofthe first conductive material.
 2. A method according to claim 1,wherein: the first conductive material and the second conductivematerial are substantially similar, and removing the unplated portionscomprises etching the unplated portions of the first conductive materialand a portion of the second conductive material.
 3. A method accordingto claim 1, wherein: the first conductive material and the secondconductive material are different; and removing the unplated portionscomprises selectively etching the unplated portions of the firstconductive material without etching the second conductive material.
 4. Amethod according to claim 1, further comprising: depositing a soldermask over a portion of second conductive material such that the soldermask defines an aperture through which light from the optical elementmay pass and such that an end portion of the second conductive materialis exposed inside the aperture.
 5. A method according to claim 4,further comprising: disposing a solar cell over the aperture; andcoupling a terminal of a solar cell to the exposed end portion of thesecond conductive material.
 6. A method according to claim 1, whereindepositing the first conductive material comprises depositing the firstconductive material on the flat second surface of the cylindricalpedestal structure such that portions of the conductive material aredisposed in four elongated radial recesses defined in the flat secondsurface, and wherein said plating comprises forming said secondconductive material over the first conductive material disposed in thefour elongated radial recesses.
 7. A method according to claim 6,wherein: the first conductive material and the second conductivematerial are substantially similar, and removing the unplated portionscomprises etching the unplated portions of the first conductive materialand a portion of the second conductive material disposed outside of saidfour elongated radial recesses.
 8. A method according to claim 6,wherein: the first conductive material and the second conductivematerial are different; and removing the unplated portions comprisesselectively etching the unplated portions of the first conductivematerial disposed outside of said four elongated radial recesses withoutetching the second conductive material disposed inside said fourelongated radial recesses.
 9. A method according to claim 6, furthercomprising: depositing a solder mask over a portion of second conductivematerial disposed inside each of the four elongated radial recesses suchthat the solder mask defines an aperture through which light from theoptical element may pass, and such that respective end portions of saidsecond conductive material disposed inside each of the four elongatedradial recesses is exposed inside the aperture.
 10. A method accordingto claim 9, further comprising: disposing a solar cell over theaperture; and coupling a terminal of a solar cell to the exposed endportions of said second conductive material disposed inside each of thefour elongated radial recesses is exposed inside the aperture.